The amount of speed gained or lost is directly proportional to how much weight you add or subtract from your arrow weight..........it has nothing to do with the design itself.

If your going from a heavy 4" vane set up to Blazers........you'll pick up a bit, going from feathers to Blazers.........you'll likely lose a bit.

Figure somewhere around 1fps for about every 3grs gained or lost. So with that model if you go from a 25gr fletchingset upto a 15gr one it would be an educated guess to figure you might pick up about 3fps.